Abstract:

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We have studied the fracture behavior of coating layer when low and high alloying
galvannealed (GA) steels are subject to forming process. To understand better powdering features in
the coating layer of the steel sheets, we carried out V-bending test and a series of finite element
analysis which simulates damage characteristics in the coating layer. Results showed that the
powdering behavior in the coating is significantly affected by the soundness and volume fraction of
phases in the coating layer. The hardness variation of coating layers attributed to different phases
leads to different deformation behavior of the coating layer itself.

Abstract: Micro-alloyed cold forging steel has been developed to rule out heat treatment process
before forging in order to save energy consumption. These non heat-treated cold forging steels
utilize the work hardening during cold working to ensure the mechanical properties. In other words,
the required strength of forged part is achieved by work hardening with the accumulation of plastic
strain during the cold working. Therefore, the plastic deformation characteristics should be carefully
understood for successful process design. Evolution of both microstructure and plastic
characteristics of micro-alloyed cold forging steel has been investigated in the present study. For the
optimization of forging processes, finite element analysis and die life predictions were carried out.

Abstract: A multiple-needle-cathode plasma surface alloying process has been developed for
improving the properties of surface hardness, wear resistance and corrosion resistance of Ti6Al4V.
The process is carried out at temperatures below 800 °C and facilitates the simultaneous introduction
of W, Mo,nitrogen and carbon into the surfaces of Ti6Al4V forming gradient alloying layer structure
with an extremely high hardness. The process is performed at working pressure of 30Pa-80Pa with
9-needle-cathode of W80Mo20 alloy rods array and a high pure graphite plate cathode as target
electrode. A maximum microhardness is 4-6 times much harder than the substrate. The results show
the presence of carbide and nitride ceramics phases contribute to high microhardness and wear
resistance. The multiple-needle-cathode discharge plasma treatment is an effective method for
improvement of the mechanical and tribological properties of titanium-base alloys by formation of
graded diffusion hard surface layers. The present paper describes this novel process and properties
characteristics.

Abstract: TiN coating was deposited on 3Cr2W8V alloy by PVD and then processed with electron beam surface alloying process. The microstructure, microhardness, friction coefficient, amount of wear and corrosion resistance of electron beam treated specimens were investigated. It is shown that the electron beam treated specimens can improve the properties of material. The coating has an average microhardness of approximately HV800, the friction coefficient of electron beam irradiation treated specimens is considerably lower than that of TiN coating. When the electron beam irradiate times is appropriate, the roughness of surface will much lower, and it will achieve polishing effects. The corrosion behavior of the composite coating in 3.5% Nacl solution at room temperature was also determined using a potentiont state system. In comparion with the corrosion potential for 3Cr2W8V alloy, the corrosion potentials of TiN coating and electron beam treated specimen are increased respectively. The electron beam treated specimen has the lowest corrosion current density as well as the highest corrosion potential showing an improved corrosion resistance compared with 3Cr2W8V alloy.

Abstract: The purpose of this research paper is focused on the high speed steel surface layers improvement properties using HPDL laser. The paper present laser surface technologies, investigation of structure and properties of the high speed steel alloying with carbides using high power diode laser HPDL. Investigation indicate the influence of the alloying carbides on the structure and properties of the surface layer of investigated steel depending on the kind of alloying carbides and power implemented laser (HPDL). In the effect of laser alloying with powder of carbides occurs size reduction of microstructure as well as dispersion hardening through fused in but partially dissolved carbides and consolidation through enrichment of surface layer in alloying additions coming from dissolving carbides. Introduced particles of carbides and in part remain undissolved, creating conglomerates being a result of fusion of undissolved powder grains into molten metal base. The structural mechanism was determined of surface layers development, effect was studied of alloying parameters, gas protection method, and thickness of paste layer applied onto the steel surface on structure refinement and influence of these factors on the mechanical properties of surface layer, and especially on its hardness, abrasive wear resistance, and roughness. It has the important cognitive significance and gives grounds to the practical employment of these technologies for forming the surfaces of new tools and regeneration of the used ones.

Abstract: Electro-spark alloying (ESA) method was used to create a coating on the surface of TC11 alloy (Ti–6.5Al–3.5Mo–1.5Zr-0.3Si wt%). The oxidation behavior of the TC11 alloy and its deposited coating was investigated in air at 700°C. The resulting structures were analyzed in great detail by metallographic analysis and by scanning electron microscopy (SEM)